The SYK model (Sachdev-Ye 1993, Kitaev 2015) has N Majorana fermions with random all-to-all q-body interactions: H = (1/4!) Σ J_ijkl ψ_i ψ_j ψ_k ψ_l. It saturates the chaos bound — the Lyapunov exponent λ_L = 2π/β (Maldacena, Shenker, Stanford 2016) — making it a maximally fast scrambler. The large-N limit is exactly solvable via the Schwinger-Dyson equations, and the low-temperature physics is described by a Schwarzian action identical to Jackiw-Teitelboim 2D gravity — establishing a rare solvable example of the holographic duality.